critical angle = [tex]i_{cr}[/tex] = 73.7°
total internal reflection = [tex]\alpha[/tex]cr = 54.58°
Given:
refractive index of core, [tex]n_{core}[/tex] = 1.46
refractive index of clad, [tex]n_{clad}[/tex] = 1.4
The incidence angle that causes the refraction angle to be equal to that at that angle of incidence is known as the critical angle.
The incidence angle needs to be greater than the critical angle for Total Internal Reflection to happen.
Now, we know that the critical angle = θcr is given by:
sinθcr = [tex]\frac{n_{clad} }{n_{core} }[/tex]
θcr = [tex]sin^{-1}[/tex] ([tex]\frac{n_{clad} }{n_{core} }[/tex])
θcr = [tex]sin^{-1}[/tex] ([tex]\frac{1.4}{1.46}[/tex])
= [tex]sin^{-1}[/tex](0.96)
=73.7° = [tex]i_{cr}[/tex]
Now for [tex]\alpha[/tex]cr:
[tex]sini_{cr}[/tex]/[tex]sin\alpha _{cr}[/tex] = 1/[tex]n_{core}[/tex]
[tex]sin\alpha _{cr}[/tex] = sin(90° - 73.7°) × 1.46
[tex]sin\alpha _{cr}[/tex] = sin(16.3°) × 1.46
=-0.558 × 1.46
=-0.815
[tex]\alpha _{cr}[/tex] = [tex]sin^{-1}[/tex](0.815)
= 54.58°
Total internal reflection means that none of the light that might conceivably travel away from this surface is refracted and that all of it is reflected.
To learn more about total internal reflection visit:
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